Hobbing machine



w. ,F. ZIMMERMANN r AL 2,857,817

Oct. 28, 1958 HOBBING MACHINE Filed Feb. 16. 1953 8 Sheets-Sheet 1INVENTORS WILLIAM F. ZIMMERMANN By GRANGER DAVENPORT ATTORNEY w. F.ZIMMERMANN ErAL HOBBING MACHINE Oct. 28, 1958 Filed Feb. 16, 1953 8Sheets-Sheet 2 IN V EN TORS WILLIAM F. Z IMMERMANN y GRANGER DAVENPORTATTORNEY w. F. ZIMMERMANN' ETA]..-

Oct. 28, 1958 HOBBING MACHINE 8 Sheets-Sheet 3 Filed Feb. 16, 1953 HOBAND WORK STOP ROTATING FIG. l4. NORMAL FEED FA'sT RETURN S NT M N R T AO N M P m m NMV I W A 2 D m M G m M u W .v v. W B L L E W f ATTORNEY 8Sheets-Sheet 4 w. P. ZIMMERMANN EIAL HOBBING MACHINE AT TORNEY} Oct. 28,1958 Filed Feb. 16, 1953 I 6 I I I I nI I I I I I H II. I u I e a w lOlOct 28, 1958 w. F. ZIMMERMANN EI'AL 2,857,817

' HOBBING MACHINE Filed Feb. 16,1953 8 Sheets-Sheet 5 9. no l if, a g

FIG. 9.

LI IT INVENTORS BY GRANGER DAVENPORT AT'TORNEY- WILLIAM F. Z IMMERMAN NOct. 28,1958 w. F. ZIMIVIERMANN EI'AL 2,357,817

HOBBING MACHINE Filed Feb. 16, 1953 8 Sheets-Sheet 7 LI L2L3 CIRCUITBREAKER HYDRAULIC MOTOR No.3 FIG. u.

CO'OLANT MOTOR No.2

MAIN MOTOR NO. I I

REVERSING SWITCH COOLANT OFF ON INVENTORS WILLIAM EZIMMERMANN y GRANGERDAVENPORT ATTOR N EY Oct.' 28,1958 I I W.-F. ZlMMERMANN EI'AL 5 nossmcMACHINE RUN JO HYDRAULIC I 3 n MOTOR a-rz 3| 2 INVENTORS WILLIAM F.ZIMNIERMANN By GRANGER DAVENPORT United States Patent Ofiice 2,857,817Patented Oct. as, 1958 HOBBING MACHINE William F. Zimmermann, Maplewood,and Granger Davenport, Montclair, N. J., assignors to Gould & Eberhardt,Incorporated, Irvington, N. J., a corporation of New Jersey ApplicationFebruary 16, 1953, Serial No. 337,007

Claims. (Cl. 90-4) This invention relates to machine tools, moreparticularly to hobbing machines, and its primary objective is toprovide a machine by which gear teeth may be produced on blanks, by agenerating process, accurately and more rapidly than has been possibleof attainment heretofore. The invention further aims to render availablea hobbing-machine organization in which a relatively large number of theteeth of the hob are caused to be simultaneously in cutting relationwith the blank, to the end, not only of increasing the production rate,but of causing wear on the hob to be distributed over substantially itsentire length so as to eliminate. the need for shifting the hob and themechanisms required to effect hob shifting.

A further aim of the invention is to render available a hobbing machineadapted more especially to cutting teeth on helical gears by a methodand arrangement which involves driving the hob and the work blank insynchronism at a constant ratio without the incremental or decrementalmotion heretofore regarded necessary in the cutting of helical gears.The invention further proposes a structure that eliminates differentialmechanisms,

the errors occasioned by differential producing means,

and the time involved in calculating lead gearing and making thenecessary gear changes. The expression differential producing means asherein used is intended to mean any device, mechanism, or method ofcontrol,

by the aid of which the hob rotation relative to work rotation isadvanced or retarded as the cutting of helical teeth on the blankprogresses.

Still another aim of the invention is to provide a hobbing-machinestructure with means whereby the axis of one of the power-rotatedmembers, preferably the hob, may be so orientated on a translatablecarriage that the hob may be caused to feed in a direction parallel toits helix, and the carriage-supporting slide so orientated on itssupport that the bodily movement of the orientated lhob may be caused tooccur in the direction of the helix to be produced on the work. That isto say, preferably the hob is journaled in a swivel head and the swivelhead, 'in turn, is mounted upon a translatable carriage whose line ofmovement is defined by guideways on an an- :gularly adjustable trunnion,the swivel axis of which parallels the swivel axis of the hob swivelhead. Preferably also, the work axis is fixed and extends in a directionthat is normal to the axes of the swivel head and of the swiveltrunnion. When these relations exist the translatory movement of thepower-driven hob may be in the direction ofthe helix of the gear to becut, and the helix of the hob may be brought into parallelism 'with thedirection of bodily travel of the hob. .This

invention among other features comprehends an organization in which theaxis of both the hob and the work are crossed and the direction of feedparallels neither axis. The invention further proposes a constructionsuch that the crossing of the hob axis and the work occurs at a commonpoint within the axial length of the hob and within the axial length ofthe work blank so that the hob enters the blank at one side of the workaxis and leaves the blank at the other side-of the work axis. The commonpoint above mentioned is, in accordance with this invention, within theplane of the work blank and coincident withthe swivel axis of thecarriage trunnion, and coincident with the swivel axis of the hob whenthe latter has been bodily shifted approximately halfway across the facewidth of the Work blank.

Still another objective of the invention is the development of a hobbingmachine capable of utilizing an im proved method and means of hobbinghelical gears, set forth more fully in our application Serial No.337,008, filed February 16, l953, which is predicated upon the principleof moving the-hob (or the work) relatively to the blank in a singlelinear path, first in one direction to produce the teeth on the blankand then in the opposite direction through the previously cut teeth toposition the hob again at the point of starting. By such single linearmovement not only are infeed transmissions eliminated, but by employinga linear cycle it is possible to decrease the floor-to-floor time of thehobbing operation in a practical, efiicient manner.

The invention further undertakes to provide a hobbing machineconstructed and arranged so that the rate of travel of one of themembers, preferably the hob, is capable, of variation, not only forbringing the tool quickly to or away from the work, but for producing achange in the rate of feed while the tool is in the cut. With a machineembodying the changeable feed rate principle of this invention, the hobis initially set to its full tooth depth radially of the work and thenfed at a relatively rapid rate in to the work. This fast feed which maybe called a plunge feed is transitory in character and continues untilthe hob is about to cut full teeth in the blank at which time the rateof feed is reduced to a normal rate of feed for the work being operatedupon, and the work blank is completed at this normal feed rate. When thehob has finished cutting, rotary motions of the hob and work arestopped, and the hob is back-tracked in its same path. By the methodherein proposed, the unidirectional transitional feed time, thefull-tooth cutting time, and the return time are materially shortenedand the saving realized and reflected in greater production.

A further objective of the invention is to embody in a hobbing-machineorganization an improved means for effecting work clamping, worksteadying, and the relative movements between the hob and the work, bywhich positive assurance is had that the Work is safely mounted beforethe feed movement can be initiated, either manually or automatically.Insecure Work clamping is inherently dangerous and it is an aim of thisinvention to avoid such hazards. In conjunction with this feature theinvention also proposes an improved system of controls for the variouscoordinated drives and movable elements, which embodies essentially twosystems, one for controlling movements when setting up the machine, andone for causing the various movements to occur in proper sequenceautomatically after the machine is set up for automatic operation, thetwo systems being coordinated but mutually exclusive so as to preventincompatible operations.

The invention further undertakes to provide a hobbing machineparticularly adapted to generate the teeth of helical gears, either leftor right hand, by a climb cutting principle in. which the hob startsfrom a position below the work and finishes cutting above the plane ofthe work, the direction of the hob rotation being such that the cuttingteeth are pulling into the work in the same direction as the hob feed.It is also proposed to provide a machine structure in which externalshafting is avoided and to enclose all inherently dangerous transmissionelements within the machine proper.

In obtaining the above objectives, and others hereinafter appearing, itis proposed to provide a machine with a main support common to the tooland the work and to effect relative bodily movement between the hob andthe gear blank, in a direction that is common to the helix angle of boththe hob and the work. When so related and shifted, the plane of the hobwill lie tilted relative to the line of its travel, and its line ofshift will be tilted relative to the axis of the work.

When such relations obtain it will be seen that if the bodily movementbetween the hob and work is caused to occur in a direction of the helixangle of the teeth to be cut on the gear and if the axis of the hob istilted 90 plus its lead angle, from the line of the tooth helix on thegear, it becomes possible to shift the teeth of the one through thespaces between the teeth of the other in a straight line directionwithout interference, and no compensation need be made for either thelead of the hob or of the work. It will also be seen that if a rotatingwormlike member is held in space at such an angle that its helix iscoincident with the helix of a rotating helical gear, and one or theother shifted bodily in that direction and with their teeth (or threads)in constant-speed meshed relation and without interference, it ispossible to reproduce teeth on a helical gear by the hobbing method, bysubstituting a hob for the worm-like member. In the case of a hob,however, the extent of bodily shift (feed) is at least equal to thelength of the tooth to be cut on the blank, and the feed will ordinarilybe from one face of the gear to the other. And since, as in conventionalbobbing, a single-thread hob is caused to revolve as many times as thereare teeth to be cut, for each revolution of the work, the straight-linefeed of a cutter of this organization can be as fast as is consistentwith the quality of tooth formation desired, and that, at the end of thecut, both the cutter and work rotations may be stopped and astraight-line return traverse of the stationary hob through the toothspaces may be instituted and continued at a very rapid rate. The machineis particularly well adapted for multiple-thread hobs, to take advantageof the increased production resulting from their use.

With a hobbing machine constructed in accordance with this invention,the teeth of the hob may be initially set at full cutting depth radiallyof the blank and be caused to enter the blank at a relatively fast feedrate, i. e., plunge-feed, until full tooth form is reached and thenslowed to a normal feed rate while both the hob and the blank arerotating together in constant speed relation (nondifferentially).

This invention thus proposes a new method and means for bobbing spur andhelical gears which comprehends a fast transitional feed followed by anormal feed of one of two power-rotated elements relative to the other,the elements being rotated in constant-speed ratio on axes crossed atselectively variable amounts, with the change in feed rate from fast toslow being caused to occur automatically when the cutter has plungedinto the work and is reaching full-tooth cutting relation with theblank.

Other objects and advantages will be in part indicated in the followingdescription and in part rendered apparent therefrom in connection withthe annexed drawings.

To enable others skilled in the art so fully to apprehend the underlyingfeatures hereof that they may embody the same in the various wayscontemplated by this invention, drawings depicting a preferred typicalconstruction have been annexed as a part of this disclosure and, in suchdrawings, like characters of reference denote corresponding partsthroughout all the views, of which:

Fig. 1 of the drawings is a side elevation of a hobbing machineembodying the invention.

Fig. 1A is a side view of a portion of the machine showing parts of thefeed trip mechanism.

Fig. 2 is front view of the machine.

Fig. 3 is a view similar to Fig. 2, but with the work table andwork-supporting column removed.

Figs. 4 and 5 are partial views of the hob swivel head, carriage, andguideways in positions assumed for cutting right-hand and left-handhelical gears, respectively.

Fig. 6 is a plan view of the bobbing machine.

Fig. 7 is a line diagram of the gear trains embodied in the machine.

Fig. 8 is a rear elevation of the machine.

Fig. 9 is a side view of the rear portions of the machine showingparticularly the hydraulic and electrical control panels with theircovers removed.

Fig. 10 is a line piping diagram of the hydraulic system and in whichconventional symbols are used to indicate the various valves controlelements and their connections.

Fig. 11 is an elementary diagram of a representative electric controlsystem for the machine.

Fig. 12 is a wiring diagram for the machine.

Figs. 13 and 14 are diagrammatic views of a representative hobbing cyclecarried out by the machine of this invention.

General structure (Figs. 1-7) Referring more particularly to Figs. 1-6,the hobbing machine illustrated comprises a number of components,including a two-level main base 50, the upper level a of which isequipped with guideways 52 adapted to support and guide a trunnioncarrier 53. The trunnion carrier is adjustable longitudinally of thebase, according to the diameter of the gear to be cut, by means of amanually operated screw-and-nut mechanism indicated at 54'.

The trunnion carrier is provided with a large annular bearing surface 55arranged to support a normally fixed but angularly adjustable trunnion56. In this instance the pivotal axis of the trunnion 56 is horizontaland is perpendicular to and intersects the projected axis of the worktable 57. The work table 57 is, in this embodiment, journaled on avertical axis in tapered bearings 58 provided in a sub-base 51 that issupported upon the lower level of the main base 50.

The front of the trunnion 56 is provided with parallel guideways 59,positioned to lie in a plane normal to the trunnion axis and parallel tothe work-table axis, and carries a translatable carriage 60. Thecarriage 60, in turn mounts an angularly adjustable hob swivel head 61that journals a hob spindle 62 and the cutter or hob C.

In the embodiment illustrated the swivel axis of the head 61 is parallelto the swivel axis of the trunnion 56, and the hob-spindle axis isperpendicular to the swivel axes of the head and the trunnion. Withthese components related as described, it is possible to adjust the hobin or out relative to the work axis, to adjust the ho! spindle axisangularly about an axis normal to the work axis, to initially positionthe hob along its axis, and to shift the hob in a plane parallel to thework axis and in a direction crossing the work axis in that plane, fromright to left as in Fig. 4, or from left to right as in Fig. 5. It is tobe observed further that in accordance with this invention the swivelaxis of the hob swivel head 61 intersects the rotary axis of the hobspindle 62 at a point lying preferably within the length of the hob, andthat, at a given point in the bodily shift of the swivel head slidealong the trunnion guideways, the hob swivel axis will coincide with theswivel axis of the trunnion and both f these axes will intersect thework axis at a point lying preferably within the face width of theworkblank to be operated upon.

Both the hob and the work are power-driven, as will be described, insynchronism but without additive or subtractive differential motions, asheretofore was customary to employ.

Hob-spindle and work-spindle drives (Figs. 1 and 7) The main spindledrive in the machine depicted comprises two interconnected trains,namely, speedor hobrotating trains and indexor work-rotating trains,both driven from a common source which is here indicated by a main motorM.

The main-drive motor M is solidly mounted upon a platform 65 supportedby the adjustable trunnion carrier 53, so that its output shaft 66 iscoaxial with the swivel axis of the trunnion 56. The motor shaft 66carries a gear 67 that meshes with a gear 68 on an offset shaft 69journaled in a bearing provided in the swivelable trunnion 56 on an axisparalleling the trunnion axis. The center distance of the shafts 66 and69 is fixed but has been so selected that the gears 67 and 68 may beremoved and replaced by others to afford a change in speed. In thepresent instance six changes in speed are contemplated.

As the angular position of the trunnion is changed, the shaft 69 andgear 68 travel around the gear 67 planetwise. The planetary shaft 69extends forward and carries a bevel gear 70 that meshes with anotherbevel gear 71 secured to a shaft 72 also journaled in the swivelabletrunnion but on an axis perpendicular to the axis of the planetary shaft69. A portion of the shaft 72 is splined, as at 73, and drives a splinedbevel gear 74 which in turn drives a bevel gear 75 mounted on one end ofa shaft 76. Shaft 76 is journaled in the carriage 60 at the axis of thehob swivel head 61, and carries another bevel gear 77 which meshes withbevel gear 78 on shaft 79. Shaft 79 is journaled in bearings provided inthe hob swivel head 61, extends diagonally in the hob swivel head, andis geared by bevel gears 80 to a worm shaft 81 also journaled in the hobswivel head. 'A worm 82 mounted on the worm shaft is arranged to drive aworm gear 83 that drives a spindle 84 with which the hob C is connected.In the arrangement described the hob spindle is power-rotated; it mayalso be swiveled about the axis of shaft 76; it may also be translatedbodily in either direction on the guideways 59 of trunnion 56, and thelatter may be swiveled about the axis of shaft 66 so that the line ofbodily shift of the hob may be vertical or slanted to the right or tothe left, to an included angle of as much as 90, and the entire assemblyfrom motor to hob may be moved toward or away from the work spindle. Itis to be noted that the swivel axis of the hob swivel head 61 intersectsthe hob intermediate its ends, and at least at one point in the bodilyshift of the hob this swivel axis coincides with the swivel axis of thetrunnion, that is, at one point shafts 76 and 66 may be coaxiallyaligned, and at all other points in the linear shift, the hob swivelaxis is to one side of the trunnion axis or to the other. Preferably thedistance of feed travel of the hob to each side of the trunnion axis isequalized, or substantially so, for reasons later to be explained.

Index train The drive to the work table 57 is derived from the hob-drivetrain and is taken from the planetary shaft 69 by means of a gear 85tight on that shaft. Gear 85 is arranged to mesh with a gear 86 mountedupon a relatively stationary parallel shaft 86a. Shaft 86a is suitablyjournaled in the bearings in the trunnion carrier at the trunnion axisand is therefore coaxial with the motor shaft 66. Gear 85 mayaccordingly roll around the driven gear 86 when the trunnion isangularly adjusted. The driven gear 86 drives a bevel gear 87 that ismeshed with bevel gear 88 on a vertical shaft 89. Shaft 89 is journaledin the movable trunnion carrier 53 and carries at its lower end a bevelgear 90 that is meshed with an internally splined bevel gear 91. Thegear 91 transmits power to a horizontal splined shaft 92 that isjournaled in table 57 and carries a change gear 94. Gear94 meshes withand drives another change gear 95 on a stub shaft 96. Shaft 96 carries athird change gear 97 thatmeshes with change gear 98 on a wormshaft 99.The worm shaft 99 extends forward and carries a worm 100 that mesheswith a worm gear 101 secured to the lower end of the work-table spindle57. Change gears 94, 95, 97, 98 are designed to be removed and replacedby others to provide a range of teeth to be cut on the workpiece,:;

the stub shaft 96 being adjustably mounted on an adjustable arm inconventional manner, to obtain propercenter distances between theselected driving and driven change gears, as will be understood.

The work index train is, it will be seen, normally connected positivelyand unvaryingly with the hob-drive train, both trains deriving powerfrom the common planetary shaft 69. Thus both hob and work are caused tobe power rotated at relatively constant rates, e. g., one revolution ofthe hob for each tooth to be cut on the blank, without an additive orsubtractive differential elfect of any kind.

The foregoing drive will be utilized during the cut but in the course ofsetting up should one desire to revolve the hob independently of thework, or conversely, revolve the work independently 'of and relativelyto the hob, a fine-tooth clutch (not shown) may be incorporated in thework index train ahead of the splined gear and j shaft 91, 92. When theclutch is disengaged the power drive to the work table is disconnected,the table may be revolved manually by applying a crank to the keyed endJ 99a of the worm shaft 99, and proper work relation to hob tooth orspace can conveniently be obtained. In the absence of the clutch, properrelation of the work with the hob tooth or space may be obtained byremoving one of the work index change gears 94-98 and the work tableadjusted as explained, or the change gears, or the hob-jogged by powerto the proper position in relation to the work.

Feed transmission In the instant embodiment of the invention, relativecorrespond, in the normal case, to the helix angle of the helical gearto be cut. When cutting spur gears, the

direction of travel of the hob will parallel the work axis and theteeth. Also, in accordance with this invention it is proposed that thefeed movement of the hob be in an upward direction during thecuttingoperation and in a downward direction for the return, and apreferred method and means for imparting linear movement to the hob inforward and reverse direction includes ahydraulic motor 105 and ahydraulic system shown in more detail in Figs. 8 and 9, anddiagrammatically in Fig. 10.

In Fig. 1, the numeral 105 indicates a hydraulic motor of the piston andcylinder type, whose piston rod 106 is secured to the hob carriage 60;the numeral 107 indicates a work-clamping hydraulic motor of the pistonand cylinder type, whose piston rod 108 is adapted to be connected withand operate a work-clamping fixture, by which work may be clamped to thetable 57, and the numeral 109 indicates another hydraulic motor of thepiston and cylinder type Whose piston rod 110 reciprocates a rack bar111 connected to actuate an outboard work-centering steadyrest 112. Therack bar 111 meshes with an idler gear 113 journaled in the outboardcolumn 114, and the gear 113 in turn meshes with a rack bar 115 carriedby the steadyrest 112. The steadyrest 112 is provided with verticalguideways fitting guides 116 provided on the face of the column 114. Thework-clamp motor 107 is located in the base of the machine and itspiston rod coaxially aligned with the work-spindle axis. The hob-feedingmotor 105 is mounted at the top of the trunnion 56 and its piston rod isparallel with the guideways 59 thereof. These several hydrauliccylinders are interconnected and controlled as will now be explained.

In Fig. 8 the letter T indicates a tank, reservoir, or collecting basinfrom which cylinder actuating fluid is derived and to which expendedfluid is returned. The letters HM indicate an electric motor connectedto drive a vane-type constant-delivery hydraulic pump PF. The pump PFtakes a fluid from the tank T and delivers it into the line marked P.

In Fig. 9 the characters AF, BE and CD indicate 4-way valves of awell-known make, solenoid-operated. Valve AF has a closed centerposition and is caused to operate without a spring. Valve BE has anopen-center position and is spring-centered. Valve CD has a closedcenter position and is spring-centered. In Fig. 10 various pos sibledirections of flows through the valves are indicated by the arrows ofthe valve symbols. In the positions of the valves shown the flows arecut off as in valves AF and CD, or bridged as in valve BE. Numeral 120indicates a sequence valve of the direct-operated type whose function inthe system is to remain closed to line P1 (as indicated) until thepressure in line P attains a predetermined operating value.

Numeral 121 indicates a counterbalance valve, directly operated, whosefunction is to permit a flow from P1 to P2 and the underside of thepiston of the carriage cylinder 105, but to check the return unless oruntil a pressure somewhat greater than the weight of the carriage existsin the cylinder 105 at the upper side of the piston. Thus, if thecarriage is being propelled upwards and there is a failure of hydraulicpower, the carriage is hydraulically locked against falling.

Numeral 122 indicates a check valve designed to prevent flow of fluidfrom line P1 to line P3 during upfeeding. During an upfeed operationvalve 122 is hydraulically connected with line P4 which at that timecarries the same pressure as line P1. The combination of pressure inline P4 and the force of the spring within the valve is greater than thepressure of line P1 directed against the head end of check valve 122.Accordingly valve 122 is held closed.

Numerals 123 and 124 indicate rate-control valves for controlling thenormal feed and the plunge-feed rates, respectively, by limiting therate of discharge from the upper end of the cylinder 105. The setting ofvalve 123 is made to provide a slow or normal rate of feed and thesetting of valve 124 is made to provide a faster rate of feed, i. e.,plunge-feed. The selective operation of these valves in the hydraulicsystem is under the control of the solenoid-operated valve CD in amanner to be explained.

Numeral 125 indicates a pressure-relief valve connected across theforward pressure line P1 and the return line P to the tank T.

Numerals 126 and 127 indicate rate-controlling needle valves in thepressure lines leading to the outboard cylinder 109.

The hydraulic symbols herein employed are those of ManufacturingEngineering Standards, February, 1951, pages 5 through 8, also known inthe industry as JIC Hydraulic Standards. The present invention is not inany one component of the hydraulic system but in the cooperativecombination, arrangement, and method of ,control with particularreference to the hobbing-machine combination described and claimedherein.

Before explaining typical setup and work cycles of 8 operation, the flowof oil will be first traced through the several control elements andactuating cylinders.

Clamping circuits and plunge-feed Starting at the pump PF, oil underpressure is fed into line P, and assuming valve AF is shifted to theright, the pressure oil flows through the valve to line 130 and branchlines 131 and 132 connected with the cylinders 107 and 109. Return oilfrom these cylinders passes through lines 133, 134, 135, diagonallythrough valve AF to tank line 1 and to the tank T. When both cylindersstall themselves under their loads, the pressure in line P will rise,and, acting through line P, will effect opening of the sequence valve sothat pressure fluid may then flow through the valve in the direction ofthe arrow, to line P1. With 4- way valve BE also shifted to the right,the pressure in line P1 flows diagonally through the valve to line P4and reacts on the check valve 122 and assists in holding that valveclosed. The increasing pressure in line P1 thereupon opens check valve136, which is built into counterbalance valve 121, and passes into lineP2 connected with the underside of the carriage operating cylinder 105.The carriage 60 thereupon moves in an upward direction and fluid fromthe large end of the cylinder passes through lines P3 to 4-way valve CD.Assuming valve CD also to be shifted to the right, the discharged fluidpasses diagonally through the valve to line 137 to the plunge-feed valve124, which has been set to limit the rate of flow to a relatively fastrate of hob feed. Fluid leaves the valve 124 by lines 138 and 138:: tovalve CD (right position) and diagonally through the valve to tank lineP5, and a portion may flow through line 138 to valve BE (right position)to tank line 1. Excessive pressure in line P1 is prevented by thepressure relief valve which operates to bypass fluid from the line P1when a predetermined maximum pressure is reached. From the foregoing itwill be seen that the work clamp motors 107 and 109 must first have beenactuated to secure the work before pressure fluid is directed to thecarriage motor 105, and only when sufficient work-clamping pressure isattained, will the carriage be actuated.

Normal feed Up-travel of the hob carriage 60 continues at theplunge-feed rate determined by valve 124 until the hob reaches fullcutting depth, at which time the carriage 60 actuates trip mechanismthat functions to restore 4- way valve CD to midposition (wherein alllines are blocked off). Oil leaving the top end of the carriage cylinder105 is thus passed through line P3, directly to the fine-feed valve 123and thence via line 139 to the plunge-feed valve 124. Fine-feed valve123 restricts the flow to the desired normal feed rate, and the flow ofoil, after passing valve 124, passes through line 138 to valve BE, tothe tank line P5. During the fine feed, the flows and pressures on theclamp motors 107 and 109 remain as described for the plunge-feed portionof the cycle.

End 0] out When the carriage reaches the end of the cutting stroke, tripmechanism is actuated which functions, as will later be explained, torestore 4-way valve BE to its midposition. This valve BE contains abridging port 140, indicated in the diagram, which operates to bypassthe pressure fluid in line P1 directly to the tank line P5. The hobcarriage thus comes to rest in its up position. Counterbalance valve 121closes for lack of sufiicient pressure in line P2 and the fluid istrapped in the small end of the cylinder 105 so that the carriage doesnot drop of its own weight. Check valve 136 also remains closed byreason of the greater pressure then existing in line P2 as against thatexisting in line P1.

Fast return After a predetermined dwell of the hob at the end of thecut, hob and work rotations are stopped and elec- 9 trical circuits arecompleted which effect shifting of 4- way valves BE and CD to theirextreme left positions. When so moved, the pressure flow in line P1'passes straight through the valve BE to line 138, thence via line 138ato valve CD and line P3 to the top end of the cylinder 105. Fluidexpelled from the bottom end of the cylinder passes back through line P2and opens counterbalance valve 121 and mingles with the flow in line P1.Thus the oil expelled from the small end of the carriage operatingcylinder 105 augments that supplied to the large end (upper end) and thehob carriage is caused to move downward at a fast return rate. As thestationary hob and work are in meshed relation, the hob may be traversedthrough the tooth spaces of the gear it had just operated upon. A smallfraction of the fluid in line P3, which is now a forward pressure line,may flow through the fine-feed valve 123 and line 137 to valve CD andtank line P5, but its volume will be small and is more than compensatedfor by the volume received into line P1 from the small end of thecarriage cylinder 105.

End of return As the carriage reaches its down position (startingposition), mechanism is tripped which effects restoration of 4-wayvalves BE and CD again to their midpositions and the pressure fluid inline P1 is passed via its bridging port 140 to tank line 2* and P5.Also, when the carriage reaches its starting position, clamp valve AF isactuated to its extreme left position. When this occurs, the flows inmotor lines 130 and 135 are both reversed, whereupon cylinder 107 isoperated to unclamp the work, and cylinder 109 operated to elevate theoutboard steadyrest 112. Needle valves 126 and 127 in the lines leadingto the outboard cylinder 109 will have been previously set to throttlelines 132 and 133 so as to effect not only the desired rate response ofthe outboard steadyrest, but also to insure operation of the main clampcylinder 107 first in the order of time.

Up traverse It it is desired to move the carriage upwardly at a traverserate, clamp valve AF can be in either its extreme right or left positionand cylinders 107 and 109 will operate in a work-clamping or unclampingdirection, respectively, as before explained. When in fully clamped orunclamped position the build-up in pressure in line P opens the sequencevalve 120 and pressure fluid is diverted into line P1. Valve BE isshifted to its extreme right position, and valve CD to its extreme leftposition, and the pressure fluid in line P1 is directed to the lower endof the carriage cylinder through lines P1, check valve 136 ofcounterbalance valve 121, to line P2. Pressure in line P1 acting throughline P4, also assists in holding check valve 122 closed. The liquidexpelled from the upper end of the hob-carriage cylinder 105, passesthrough line P3 to valve CD, thence through lines 138a and 138 to valveBE and to tank line t and P5. As the cylinder discharge is unrestrictedby being shunted around the rate-control valves 123 and 124, thecarriage will travel upwardly at a rapid traverse rate.

From the foregoing it will be observed that among other features of thisinvention, the work is clamped hydraulically and must always be securelyclamped, when so desired, before there can be a diversion of pressurefluid to propel the carriage, also that the rate of travel of the hobslide is controlled by regulating the rate of cylinder discharge, threedifferent rates of travel in one direction and a fourth rate in theopposite direction may be provided, all obtained from the one source ofpower. The clamp valve AF, the selector valve BE, and the rate valve CDare, as has been previously indicated, solenoidoperated.

Hob-slide trip mechanism As shown more clearly in Figs. 1 and 1A, theautomatic tripping mechanism that controls rate and direction mentaryform in Fig. 11.

of movement of the carriage 60 includes a pair of telescoped rods 150and 151, each of which is adapted to be, actuated by the carriage tomake or break certain control circuits. The rod 150 is in the form of atube, the upper end of which enters a housing 152, that in this instanceforms a part of the support a of the hydraulic feed cylinder 105. Thetube carries a leafspring extension 153 positioned to actuate limitswitches LS2 on an upward movement and LS3 on a downward movement. Thetube and its extension are normally held in an intermediate position byopposing springs 154 and 155 that react against the housing 152 and leafspring 153 and adjustable collar 156 on the tube. The lower part of thetube 150 carries a second adjustable collar 157 and between the twocollars, a lug 60a on the carriage is caused to operate, engaging one orthe other 'at the end of its preset travel.

7 The inner rod 151 also extends into the housing 152 and is arranged toactuate limit switch LS1 mounted in the housing. The rod 151 iscounterbalanced by opposed springs 158 and 159 that react against atrunnion extension 56a and retaining rings carried by the rod.

The carriage 60, in addition to the lug 60a also carries a spring-loadedplunger 60b whose rounded end is positioned to engage an adjustablecollar 160 on the rod 151 and after actuating the rod, to ride by,Briefly, the operational cycle is as follows: when the carriage 60 is inits lowest preset position, lug 60a is engaging collar 157 and holdinglimit switch LS3 closed. Carriage plunger 60b is below trip collar 160.When the up travel of the carriage is instituted, it moves up at aplunge-free rate until the slide plunger 60b engages and actuates tripcollar 160 on rod 151 to close limit switch LS1. Thereupon, the carriagecontinues its up travel at a normal feed rate until the carriage lug 60aengages Electrical control circuits The wiring diagram for the machine,including the power lines, contractors, and motors for the varioustransmission trains and pumps, is illustrated in its ele- The lowerright portion of Fig. 12 illustrates a control panel CP and anarrangement of the control panel buttons by which the various movementsand actions may be instituted and controlled.

The operator, having determined the speeds and set the swivel trunnion56 and the hob swivel head 61 to the required angle for the gear to becut and the hob to be used, loads the Work blank on the work table 57and replaces a U-collar 108a on the draw rod 108 of clamp motor 107.

At the start of an automatic cycle of operation, it will be understoodthat the carriage 60 is down and limit switch LS3 is closed.

Automatic cycle (Figs. 1, 1A, 10, 11 and 12) To cause the machine ofthis invention to perform a complete hobbling cycle the operator willthen proceed as follows:

A. Turn Hydraulic switch to On position which completes a circuitbetween main line Z and lines marked 1 and 2. Line 1 energizes contactorcoil 3C of contactor 151 for hydraulic-pump motor HM and theconstant-delivery pump PF starts delivering oil into the system.

B. Turn Run-Jog pushbutton switch 166 to Run position. (Normally thejogging contacts of this switch are closed as indicated in Fig. 11 andform part of a holding circuit for the main-motor starter coil 1C.) Thisswitch is a commercial item and is equipped with a cam that is turnedwhen the button is turned from Run to Jog and latches the joggingcontacts open.

C. Coolant-motor selector switch 167 is turned On, which completes aportion of the circuit to coil 2C of the coolant motor starter.

D. Selector switch 168 is turned to Auto which closes the main controlcircuit between lines 8 and 17 and opens the circuit to line that formsan essential part of the control circuit provided for manual operation.

E. Work-clamping selector switch 169 is turned to Auto, which opensparts of the control circuits that are used when clamping and unclampingthe work under manual control.

The operations A thru E above, are performed as part of setup operationsand before the operator loads a workpiece. When the operator loads aworkpiece the hob carriage 60 will be down and the boss 60a thereofagainst the stop collar 157 and switch LS3 is held closed. After loadinga blank upon the work table 57 and inserting Ucollar 108a about thedraw-rod 108 of the work-clamp motor 107, the Run button 166 is pressed.

When the Run button 166 is pressed, the following circuits are made:

(1) A circuit is completed through lines 2, 3, 4, 5, 6, LS3, 7, and 9 tothe main motor contactor coil 1C and through switch 167 and 10 to thecoolant-motor contactor coil 2C and these motors operate to drive thework table 57 and hob spindle 84 and to provide a cutting compound orcoolant to the hob. Operation of the coil 1C closes switch marked H andcompletes a holding cir cuit, through Run-Jog pushbutton 166, thuscontinuing electric power in line 7. Power is brought to the Run- Jogswitch through a pressure switch PS between lines 2 and 3, a safetyswitch built into the reversing switch 175 between lines 3 and 4, and aStop switch between lines 4 and 5, all in series.

(2) Control relay CR1 is energized, through lines 7, 12, 13 and 14, andcloses relay switch crl between lines 2 and 12 for a holding circuit,and another switch crl between lines 2 and 42 to energize solenoid coilSOL.A which effects shifting of the clamp valve spool to the right, thusconnecting the right circuit 130 with fluid pressure. Fluid underpressure supplied by pump PF is thereupon directed to the clamp motors107 and 109 as previously explained.

(3) Control relay CR2 is energized, through lines 7, 12, 16 and 18,which closes switch 012 between lines 12 and 17, also closes anotherswitch 012 between lines 17 and 19, 20, 21, leading to solenoid coilSOL.B of valve BE, and also closes another switch cr2 between lines 17,23 and 24 to solenoid coil SOL.C of valve CD, and opens normally closedswitch 012 between lines 17 and to control relay CR6 so that the workwill not be unclamped until the cycle is completed. When solenoids SOLBand SOL.C are energised, the spools of their respective valves bothshift to their right positions whereupon fluid is permitted to dischargefrom the upper end of the carriage feed cylinder 105 via valve 124 andthe carriage moves up at a plunge-feed rate after the work is clamped.The cutter, or hob, starts into the work blank at this relatively fastrate, and hobbing of the gear continues at this fast rate until the hobreaches full cutting depth, at which time (4) The carriage plunger bengages dog 160 and elevates rod 151 a sufficient distance for it toactuate limit switch LS1 to closed position. The closing of LS1completes a circuit between lines 17, 25, 26 and W of control relay CR3.Actuation of CR3 closes switch cr3 in its holding circuit between lines26 and W, and opens normally closed switch cr3 in the circuit 17, 01-2,23, 24 of solenoid SOL.C. When SOL.C becomes deenergized, the valve CDshifts automatically to its mid- 12 position and blocks the flow fromlines P3 to 137 and plunge-feed valve 124. The discharge from the feedcylinder is then shunted through the fine-feed or normal-feed valve 123,as previously explained, and the hob continues upfeeding at the normalfeed rate and carriage plunger 60b rides by dog 106.

(5) The hob continues upfeed at the normal rate until the work blank isfinished, whereupon the carriage lug 60a engages collar 156 and liftstube until leaf spring 153 engages and actuates limit switch LS2 to csed ncsition. When LS2 closes, a circuit is completed in lines 17, 27and 28 of control relay CR4, which on being energized, closes switch 04in its holding circuit, opens normally closed switch cr4 in the circuitof solenoid SOL.B, opens normally closed switch a l in the circuit tomotor contactors 1C and 2C and the rnai11drive and coolant motors stop,opens normally closed switch 0-4 in the circuit of control relay CR2,and energizes control relay CR-Ty. When S OL.B is thus tie-energized atthe completion of the upfeed, the valve automatically shifts to itscentered position (pressure fluid in P1 is then bypassed to the tank).The energizing of control relay CR-Ty closes switch cr-zy between lines17 and 30, 31 and 32 of control relay CR5. (The circuit to relay CR5 iscompleted at the expiration of a time period during which the hob dwellsin its upper position.) At the expiration of the time period CR5 isenergized and closes switch cr5 in a holding circuit around cr-ty andcloses two switches cr5 in the circuit between lines 5 and 33 ofsolenoid SOL.E, and between lines 5 and 34 of solenoid SOLD. When SOLEand SOLD are energized the spools of the respective valves CD and BE areshifted to their extreme left positions whereupon pressure fluid isdirected, as above etplained, to the upper end of the carriage cylinder105 and the carriage is propelled downwardly at a rapidtraversc rate.

(6) The carriage continues downward travel until the hob clears theunderside of the finished gear at which time the carriage lug 60aengages collar 157 and actuates the tube 150 downwardly to actuate limitswitch LS3. When LS3 is operated, the normally closed side thereof opensand breaks the circuit to control relay CR5 which opens switches crS inthe circuits to SOLD and SOLE. Valves CD and BE move to theirmidpositions under the action of their centering spring and down travelof the carriage stops. The normally open side of LS3 closes to completea circuit to control relay CR6, and the latter on being actuated, closesswitch cr6 in its holding circuit, and opens normally closed switch cm)in the circuit control relay CR1. When CR1 dcenergizes, it opens theswitch cr1 in the circuit to SOLA of the clamp valve AF. Actuation ofrelay CR6 also closes switch 016 in the circuit to SOLE and the clampvalve AF hifts to its extreme left position and pressure fluid in line Pactuates the clamp motors 105 and 109 in an unclamping direction.

(7) With the cutter and work stationary, the carriage down, and the workunclamped, the operator may change workpieces and repeat the cycle.

Manual operation The control system for this machine is designed so thatit is possible to effect operation of the main drive, work clamps, andcarriage movements, independently of one another. This is an advantagein setting up the machine for new work the first time, and for clarity,the method of controlling the several elements will he explainedseparately in the order mentioned.

Main motor M T he main-drive motor M is of the reversible type and itsdirection of operation is controlled by a reversing switch 1'75 (drumtype) which may be actuated by a handle 176 (Fig. 9). Ordinarily, thedirection of rotation is not'changed but when the hob swivel head isswiveled from left-hand to right-hand helical-gear cutting and it isdesired to have the hob spindle continue to revolve in the direction forclimb cutting, the motor rotation must be reversed due to thereorientation of the hob-spindle axis through approximately 180. Such achangeover is not a frequent occurrence and it is a simple matter to setthe drum switch manually as the occasion requires. Also, by using areversing switch and presetting it for the motor rotation desired, onlyone main starter switch is required which makes for a more simplifiedelectrical control system.

To start the main-drive motor M, the selector switch 168 is turned toSetup; the automatic-cycle control, initiating with line 17, therebybecomes dead, and another circuit is made from line to line 15 andcontrol relay CR8. Energization of CR8 closes switch cr8 between lines 6and 7 around limit switch LS3 in the circuit to the main-motor startercoil 1C. Thereafter, the main-motor M may be started by pressing the Runbutton 166 and be stopped by pressing Stop button 172. Pressing of theRun button 166 completes a circuit through lines 2, 3, 4, 5, 6,switch'cr8, lines 7, 9 to main-motor starter coil 1C. Actuation of themain-motor starter closes switch H in lines 7, 8 and completes a holdingcircuit through the jogging contacts of the Run-Jog switch. Pressing theStop button 172 opens this circuit and the motor M stops.

Main-motor jogging circuit This circuit includes the Jog portion ofRun-Jog button 166 which is connected to line 5 around Run portion ofbutton 166 and switch marked H between lines'8 and 7. (Normally thejogging contacts are closed as indicated in Fig. 11 and form part of aholding circuit for the main-motor starter coil 1C.) This button isequipped with a cam which is turned when the button is turned from Runto log and latches the jogging contacts open. Hence when button 166 ispressed, a circuit is completed thru lines 5, 6, 7, 9, to 1C andinterrupted when the button is released and the main motor runs only aslong as the button is held down.

Work-clamp and support-arm operation For work-clamp cylinder operations,the clamp selector switch 169 is turned to its On position which closesthe circuit lines 2 and 43 to solenoid SOL.A. The valve AF thereuponshiftsto the right and pressure fluid is directed to cylinders 107 and109 which respond in a work-clamping direction. With switch 169 in theOn position the circuits through line 2, switch cr6 and lines 40 and 41to solenoid SOLF and through line 2, switch crl and lines 42 and 43 tosolenoid SOL.A are opened which prevent the automatic operation of thesolenoids and valve AF.

To unclamp the Work and raise the support arm 112 the clamp selectorswitch 169 is turned to Off which closes the circuit between lines 2 and41 to solenoid SOLF. The valve AF thereupon shifts to the left andpressure fluid is directed to cylinders 107 and 109 Which respond in awork-unclamping direction. With switch 169 in the Off position thecircuits through line 2, switch c'r6 and lines 40 and 41 to solenoidSOL.F and through line 2, switch crl and lines 42 and 43 to solenoidSOL.A are opened-which prevents the automatic operation of the solenoidsand valve AF.

It will be observed from Fig. 11, there is one control system includingline 2, for an automatic cycle and other independent coordinated butmutually exclusive control systems for the several operating parts andfunctions of this machine.

Carriage traverse (hydraulic cylinder 105) the circuit between lines 5and 15 to control relay CR8. The energization of CR8 cloies switch 018in the circuit between lines 5 and 37 and the Up and Down pushbuttonsand 171. When the Up button 170 is pressed, a circuit is completedbetween line 37, down switch 171, lines 39, 34 and 21 leading tosolenoids SOL.D and SOL.B, respectively, whereupon valve CD is shiftedto the left (Fig. 10) and valve BE shifted to the right. The shifting ofvalve BE to the right from its normal midposition cuts off the pressureline P1 from return line P5 and directs the fluid to the underside ofthe piston of the carriage cylinder 105. Simultaneously the dischargefrom the cylinder in line P3 is caused to bypass rate-control valves 123and 124 and flows thru valve CD to lines 138a, 138 and diagonallythrough valve BE to line tank lines I and P5. Up-travel of the carriageproceeds at a rapid traverse rate so long as the Up button is helddepressed or until the carriage lug 60a engages trip dog 156 andactuates limit switch LS2. When LS2 is actuated, the circuit of SOL.B(line 22) is opened and the valve BE shifts to midposition whereinpressure fluid in P1 bypasses through the bridging port in the valvedirectly to the tank line P5, and up-travel of the carriage ceases. Thesame occurs when the operator releases the Up button 170 and both valvesBE and CD return to their midpositions.

For down-travel of the carriage, the Down button 171 is depressed.Button 171 receives current through the Up button 170 only when thelatter is in released position, so that the two buttons cannot beeffective simultaneously.

Assuming the Up button is released a circuit is completed between lines37 and 38 to the Down button 171, and when the latter is pressed, acircuit through line 31 to control relay CR5 is made. This circuit isbroken if the operator releases the Down button or when the carriagetravels down to the point wherein its lug 60a engages adjustable stop157 and actuates limit switch LS3. When this occurs the normally closedside of LS3 opens the circuit of line 32 of control relay CR5. However,when CR5 is energized, switch cr5 in the circuit 5, 33 to SOL.B iscompleted and valve BB is shifted to the left (Fig. 10), also switch crSin the circuits 5, 34 to SOLD is completed and valve CD shifts to theleft (Fig. 10). When both valves are in their left positions, pressurefluid in line P1 is directed through valve BE to lines 138 and 138a tovalve CD, thence through valve CD to line P3 and the upper end of thecarriage cylinder 105. Fluid discharged from the small end of thecylinder 105 passes through line P2, counterbalance valve 121 andmingles with that in line P1. The differential action of cylinder 105thus causes the rapid descent of the carriage 60, until it is stopped bythe trip dog 157 or by the operator releasing the Down button 170.

The main service lines are brought into the panel and connectedto theinput terminals of the circuit breaker 200 at L1, L2 and L3, and theoutput lines 1L1, 1-L2 and 1-L3 connect with the different starterswhose coils are marked 1C, 2C, 30. Lines 1-L1 and 1-L3 also feed theprimary winding of atransformer 201 whose secondary winding is groundedas at W, and the other line X leads to a fuse 203. The output side ofthe fuse connects at Z to terminal strip 204. Lines Z and W form themain bus lines of the control circuits of all the solenoids, relays, andswitches of the electrical control system.

The output side of the main-motor starter has lines 1-T1 and 1-T3connected with the reversing drum switch 175, and line 1-T2 connectedwith the motor. Lines S1 and S3 from the drum switch also connect withthe motor and it is these latter two lines that are reversed when thedrum switch 175 is turned from Forward to Reverse motor operations. Toguard against failure to throw the drum switch completely to its Forwardor Reverse position, means have been provided in the form of a safetyswitch 205 between lines 3 and 4 in series 15 with but ahead of theRun-Jog and Stop buttons 166 and 172. The switch 205 is part of the drumswitch 175 and is caused to open when the drum switch is actuated, thusbreaking the circuits in the entire control system, excepting only theclamp and unclamp circuits of valve AF.

Figs. 11 and 12 also show another safety switch PS connected betweenlines 2 and 3. This switch is normally open pressure switch that iscaused to respond to its closed position when the fluid pressure inpressure line P attains a preselected minimum value. Accordingly, thehydraulic pump PF must first be operating and sufficient fluid pressurebuilt up in the system before any of the electrical controls mayoperate, excepting again the manual control of the valve AF for thework-clamp cylinders. Also, should for any reason there be a failure inthe hydraulic power the pressure switch PS automatically opens andinterrupts any and all circuits, and the machine, if running, stops. Thepressure switch PS is located in the hydraulic panel 181 and its leads 2and 3 join with those of the valve solenoids A, F, B, E, C and D andenter the electrical panel 180 as a single cable 186.

Control panels (Figs. 8, 9 and 12) In Fig. 9, the electrical controlpanel is indicated at 180 and the hydraulic control panel at 181. M isthe main-drive motor, CM the coolant motor, and HM the hydraulic-drivepump motor, PF is the constant delivery hydraulic pump that receivesfluid from the tank T through line 182 and delivers it by line P to theinterior of hydraulic panel 181. The covers for the panels 180 and 181have been removed so that the relative positions of the various relaysand valves may be seen.

The electrical control panel 180 houses all the relays and switchesdescribed, except the limit switches LS1, LS2, and LS3 and thepushbutton switches which are located on panel CP. This control panel C?may be mounted at a convenient spot on the machine, preferably on theoutboard support column 114, and the connections made to the main panel180 by means of a cable 183. Connections from the limit switches LS1,LS2, LS3, are made by a flexible cable 184 leading to the main panel180. The several motors M, CM and HM have their wires leading into thecontrol panel as indicated in Fig. 12 and connected to theircorrespondingly numbered terminals of their respective starters.

A representative hobbing cycle is shown diagrammatically in Figs. 13 and14 in which W represents the work and C the hob. At the start of thehobbing operation, the hob is set radially of the work the full depth ofthe teeth to be cut and in a position below the workpiece as indicatedin dotted lines in Fig. 14. The trunnion will have been swung andclamped at the angle, relative to the work axis that coincides with thehelix angle of the teeth to be cut. The axis of the hob will have alsobeen swiveled to compensate for its lead whereby to position the helixof the cutting teeth in alignment with the oblique line of shift of thehob carriage. As viewed from the center of the work table, the hob is,in accordance with this invention, caused to be driven top coming sothat it tends to climb the workpiece.

When the machine is otherwise ready for operation, the Run button ispressed and both work and hob are caused to be driven in constant speedratio. Simultaneously, the up travel of the carriage is instituted andthe hob moves diagonally upwards at a relatively rapid feed rate andplunges into the work at this rate. When the hob reaches its fullcutting depth, indicated at f in Fig. 14, the plunge-feed rate isautomatically reduced to a normal feed rate, and the diagonal upfeedcontinues at the reduced rate. As the hob completes the cut and is clearof the work, both hob and work rotations are stopped, and after amomentary dwell of the hob in the up position, the down travel of thehob is instituted and the now stat 1.6 tionary hob moved diagonallydownwardly through the tooth spaces in the blank at a relatively rapidrate and comes to rest at the underside of the work. The operator thenchanges workpieces and the machine is at once ready for another hobbingcycle.

Without further analysis, the foregoing will so fully reveal the gist ofthis invention that others can, by applying current knowledge, readilyadapt it for various utilizations by retaining one or more of thefeatures that from the standpoint of the prior art fairly constituteessential characteristics of either the generic or specific aspects ofthis invention, and therefore such adaptations should be, and areintended to be, comprehended within the meaning and range of equivalencyof the following claims:

Having thus revealed this invention, we claim as new and desire tosecure the following combinations and elements, or equivalents thereof,by Letters Patent of the United States:

1. A hobbing machine having in combination a main base member, a workspindle rotatably journaled on a vertical axis in the base member, saidbase member having horizontal guide ways along an upper surface thereofextending radially of the axis of the work spindle, a stanchion membermounted upon the guideways of the base and adapted for movement thereonelectively toward or away from the work-spindle axis, a main drive motormounted on and movable with said stanchion member for driving said workspindle, a slide member rotatably mounted in said stanchion member, saidslide member having guideways extending normally parallel to the axis ofthe work spindle for the hobbing of spur gears but being angularlyadjustable relative to the stanchion about an axis normal to the axis ofthe workspindle for the hobbing of helical gears, a hob carriage mountedfor movement along the guideways of said angularly adjustable slide, ahob-spindle rotatably journaled to said carriage, and drivingconnections between said stanchionmounted main motor and said hobspindle for rotating the latter in all positions of angular adjustmentof the slide relative to the stanchion and in all positions of travel ofthe hob-spindle-carriage along the slide guideways, and meansoperatively connected with the hob carriage and movable with saidstanchion member for imparting a progressive feed movement to the hobcarriage along the guideways of the said angularly adjustable slidewhile performing the hobbing operation.

2. The combination of claim 1 in which the rotatable hob spindle ismounted for angular adjustment relative to the carriage about ahorizontal axis so that the axis of the hob spindle may be inclinedrelative to the path of movement of the carriage along the slide and thepath of movement of the carriage and hob spindle inclined relative tothe axis of the work spindle.

3. The combination of claim 1 in which the means for moving the hobcarriage along the slide guideways comprises an auxiliary motor mountedon the angularly adjustable slide member and angularly adjustabletherewith, and in which the driving connections between the said mainmotor and the hob spindle includes change-ofspeed gearing.

4. The combination of claim 1 in which the drive connections between thestanchion-mounted motor and the angularly adjustable hob spindle includea drive gear journaled on a relatively stationary axis and a driven gearjournaled in said angularly adjustable slide member on an offsetparallel axis, said gears maintaining their meshed driving relation inall positions of angular adjustment of said slide member in and relativeto the stanchion member.

5. The combination of claim 1 in which the drive from thestanchion-mounted main motor to the relatively stationary work spindleincludes a drive gear journaled on a relatively stationary axis in thestanchion member, a driven gear journaled in the angularly adjustableslide member as to be angularly adjustable about the axis of the drivegear, a drive shaft journaled in the slide member 17 for conveyingmotive power from the said driven gear to the hob spindle, a third gearon said drive shaft, a fourth gear journaled on a relatively fixed axisin said shiftable stanchion member and in mesh with said third gear, anddriving connections between said fourth gear and the work spindleincluding a splined connection in the drive between the fourth gear andthe Work spindle operative to transmit the power from thestanchion-mounted main motor to the work spindle in all positions ofadjustment of the stachion and the said motor along the base member.

References Cited in the file of this patent UNITED STATES PATENTS1,208,532 Fawcus Dec. 12, 1916 18 Warner et a1. Dec. 12, 1944 DavenportApr. 24, 1945 Praeg Mar. 6, 1951 Miller July 24, 1951 Praeg May 27, 1952FOREIGN PATENTS Australia Apr. 30, 1951 France Mar. 17, 1954 OTHERREFERENCES Gear Cutting Machinery; copyright 1909, by Flanders. TJ187F5,pages 173-175.

